1. Field of the Invention
The present invention relates to a frame structure for an image forming device and frame assembly method.
2. Background Information
An image forming device such as a copying machine or printer is equipped with a photosensitive drum, a developing unit that includes a developer, a transfer unit that includes a transfer belt and so forth, a fusing unit that includes a fusing device, and a feeding unit for feeding paper. Each of these units is supported by a frame consisting of a base plate attached to the bottom of the device and a pair of side plates fixed to the base plate.
A conventional frame structure for an image forming device is disclosed in Japanese laid open patent publication 2002-189324. This frame has a base plate, a pair of side plates fixed to the base plate with a predetermined space, and a back surface state connecting the pair of the side plates. Components for image formation, such as the photosensitive drum, are supported between the pair of side plates.
A bent portion that is bent outward on the bottom of the side plates is formed on a conventional frame structure for an image forming device as disclosed in the above publication. This bent portion abuts against the top of the base plate and the two are fixed together by screws using an electric screwdriver or the like from the top.
With this type of frame structure, an electric screwdriver cannot be used to tighten the screws when the width of the bent portion on the bottom of the side plates is narrow, and thus workability is poor. Therefore, a width of 50 mm must normally be secured in order to attach the bent portion to the side plates.
However, there is one problem, in that widening the width of the outward protrusion of the bent portion in order to attach to the side plate requires that the size of the base plate must also be increased the same amount, thereby increasing the overall size of the image forming device.
The conventional frame structure provides support by aligning a pair of side plates using knock pins or the like for alignment against the base plate, then positions the components for image formation to the pair of side plates. The pair of side plates are mutually positioned through the base plate accordingly, and measurement error is already included between the pair of side plates for the time of base plate attachment. Further, the components for image formation are supported by a pair of side plates that include attachment error in this same manner, resulting in further errors being generated at the time of attachment, and causing an accumulation of errors. For this reason, the conventional device has required significant management of assembly errors and manufacturing errors for each component.